This invention relates to a fuel injection system for a mixture-compressing spark-ignition internal combustion engine.
According to our copending U.S. patent application Ser. No. 915,676, now U.S. Pat. No. 4,243,002, the fuel dosing to an internal combustion engine is cut off as soon as coasting commences in order to prevent excess fuel consumption and the formation of particles of detrimental material in the exhaust gas, and also to avoid an uneven performance. In order to obtain reliable fuel cut-off, the valve in the bypass duct is actuated only if all criteria of the coasting operation exist, that is to say, an engaged clutch, engaged gear, closed throttle valve and an engine speed which is above the idling speed.
It has now been shown that in spite of the fuel supply being cut-off, uneven ignition can still occur in the initial operational phases of coasting, as a result of a slight fuel residue present in the suction pipe or in the internal combustion engine, and this can lead to a sequence of combustion which is uneven and which considerably disturbs the operation of the internal combustion engine.
The object of the invention is to modify the mode of operation of an internal combustion engine having a fuel injection system as described in copending U.S. patent application Ser. No. 915,676 in such a way that combustion during coasting is more efficiently checked.
Broadly speaking, the invention provides a fuel injection system for a mixture compressing spark-ignition internal combustion engine having continuous fuel injection, comprising a suction pipe; a throttle valve located in said suction pipe; a member upstream of said throttle valve, said member being actuatable by air flowing through said suction pipe so as to dose fuel to the engine; a duct which by-passes said throttle valve; a duct valve located in the duct which closes off the duct when the throttle valve is closed and when the engine speed is above the idling speed, said duct valve being operatively connected to a switching member for switching off the ignition system of the engine when said duct valve is in its shut-off position.
By means of the invention, it is possible to prevent combustion when the coasting operation of the internal combustion engine starts, so that a smooth running of the internal combustion engine is ensured. Actuation of the switching member directly by the duct valve has the advantage that ignition is cut-off reliably and simultaneously with the shutting-off of the fuel supply.
Preferably, the switching member is located in the primary circuit of the ignition system, or in the line between the high-voltage generator and the contact breaker.